18' throw is a long distance to an average size screen but need to know the screen size for an accurate suggestion. Generally the 4000/5000/6000 series of Epson's have very similar throw/shift range. The 3000 series are less but still have a decent range. The refurbished 5040 is the best bargain right now if you can find one. A refurbished 5030 should be as good or better then your current 8500. The Sony 45es is a very good 1080p projector if you prefer new but again check throw as it is a little less then the 8500. JVC is also a more expensive option. Nothing other then Epson, Sony or JVC will have the contrast of your current Epson.
"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS